Home Blood Pressure: Measuring It Right

A blood pressure reading taken in a clinic is one number from one moment, often after a drive, a wait and a walk down a hallway. A week of readings taken at home, the same way each time, tells us far more about what the arteries live with day to day. That is why we ask members to measure at home. A careless reading can be off by 10 or 20 points, enough to start a medication nobody needed or to miss one somebody did.

The cuff and the setup

Start with an upper arm cuff, not a wrist cuff. Wrist devices read high or low depending on where the hand sits.

Cuff size matters more than people expect. The inflatable part should wrap around roughly 80 percent of the upper arm. A cuff that is too small squeezes a smaller area and has to push harder to close the artery, so it reads high, sometimes by 10 points or more. If your arm measures over about 13 inches around, you likely need a large cuff.

Then the position:

• Sit in a chair with your back supported and feet flat on the floor, legs uncrossed. Crossed legs and an unsupported back each add a few points.
• Rest the arm on a table so the cuff sits at the level of the heart. An arm hanging at your side reads high.
• Sit quietly for five minutes first. Talking during a reading can raise it by about 10 points.
• No caffeine, exercise or nicotine in the 30 minutes before, and empty your bladder. A full bladder raises the number.

Two readings, twice a day, for a week

Take two readings one minute apart and write both down. The first is often a little higher. Do this in the morning before any medication, food or coffee, and again in the evening before bed.

Keep it up for seven days, then drop the first day, which is usually the least settled, and average the rest. That average is the number we work from. One high reading on a Tuesday night after an argument does not mean much. Twenty four readings over six days that average 138 over 86 mean a great deal.

We use 130 over 80 as the line, the same cutoff as the current US guidelines. Home readings tend to run a little lower than office readings, so a home average at that line counts.

Bring the monitor to a visit once so we can check it against ours, because a cuff that reads five points off quietly misleads everyone.

High blood pressure damages the heart, kidneys and brain for years without a symptom, and a weekly home average is the cheapest way to see it coming. That's the kind of thing we measure, and we teach the method before we read the numbers.

This article is educational and is not medical advice.

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